Over the 20th century, GDP growth was mainly driven by total factor productivity growth. Since the mid-2000s, however, productivity growth has been in decline. This column explores the history and future of growth focusing on four developed economies: the US, the Eurozone, the UK, and Japan. Simulated scenarios for the 21st century show a wide range of potential growth outcomes, dependent on whether total factor productivity growth stays indefinitely low, and whether the digital economy delivers a new productivity growth wave.